Will the placement of casters on speaker stands degrade the performance

Despite no knowledge, I suggest you consider the effects of metal against metal bearings and other parts.  That cannot be a good thing. Maybe we could come up with something that is based on using damping fluid for tone arms.  I actually put a teeny dollop on a pal's old Grace 707, and it helped.

I have Harbeths on Sound Anchor stands.  I took out the spikes and replaced them with round headed "carriage" type screws.  Now I can move my spealkers around wthout poking holes in my floor.  No degredation of sound.  Note:  high quality vinyl flooring directly on concrete.

The reason you got the Mye stands were to keep those panels from moving, they sure do move. A lot!
When I got my 20.1's I had a smaller space and when I wanted to listen to them, I would just move them to where they sounded the best, not a big deal. There is a difference in sound when those panels are stiffened with support,  how much support will they have on rollers...

@johnspain--I faced the same problem with a pair of Rockports and used casters under thick mdf just to move--they locked as jjss49 said--when i found the location they sounded best i removed the mdf with casters and put symposium acoustics platforms there--(took 2 of us) --yes they sounded better with the casters gone but i don't know if that was the mdf, the casters themselves or the casters having raised the height or some combo of all 3-- but in the end i felt sure that the location was ideal--so don't worry about it--i suspect where they sound best with casters is where they'll sound best without them as well.  Good luck.